Potential energy of a molecule adsorbed in synthetic zeolites. Application to the analysis of infrared spectra. 2. Potential energy of the nitrous oxide molecule adsorbed in the cavities of the zeolite NaA. Interpretation of the adsorbed nitrous oxide infrared spectra

Abstract

The potential energy of the N20 molecule in the zeolite NaA has been calculated from the evaluation of its electrostatic, dispersion, and repulsion components for different positions and orientations of the molecule. We thus obtain the positions and depths of the potential wells. The potential barriers to translation and rotation are very high and the molecule performs librational and translational oscillations inside the well, the frequencies of which have been calculated. We also evaluate the lifetime of the adsorption and the time of residence of the molecule in the well. The observed far-infrared spectra may account for the calculated frequencies. As regards the vibrational spectrum, the splitting of v1 is interpreted by the two possible orientations of the molecule N2O: the profile of the v3 band and its variation with temperature can be explained by the frequency distribution due to translation.

Vibrational Stark effect and vibrational static electric properties of N2O

“…Finally, the u3 stretching frequency behaves just opposite to v1. It is worth noting that the vl band shows the largest changes due to the electric field, as was already mentioned in the experimental results [17,21]. Although large effects are found also for the v 3 band, they are not so important, as reflected in the vibrational Stark tuning rates presented in Table 11.…”

“…Whereas Cohen de Lara and Vincent-Geisse studied theoretically the behavior of the IR bands of N20 [21], Grodzichi et al [22] carried out a simulation of the N20 molecule when absorbed in front of Ca2+ in zeolite A, using two possible linear orientations. In their work, the SCC-xa method was applied to calculate the electronic structure, whereas a valence force-field model was employed for the normal coordinate analysis of the free and absorbed molecules.…”

Spontaneous electric fields in films of CF3Cl, CF2Cl2and CFCl3

“…This symmetrical part is expressed as a constant term, E sym , plus a dipole-dipole term, parameterized through E sym z(hm z i/m) 2 reflecting the fact that all such interactions, dipole-image charge, extended dipoles and arrays of dipoles, follow this squared relation. [19][20][21] Physically the dipole-dipole term represents the tendency to hinder relative intermolecular rotational motion.…”

A review of recent progress in understanding the spontelectric state of matter

“…Thus cos -1 (<z>/) gives the angle to the normal of the average dipole, leading to the angles of 84.5 o to 87 o mentioned above. The (<z>/) 2 form, adopted to describe dipole-dipole interactions, reflects the fact that all such interactions, involving dipole-image charge, extended dipoles and arrays of dipoles, follow this squared relation [12,13,14]. We note that the symmetrical part of the contribution to Ez is related to the 'local field' at any molecular site, as defined in standard texts [15].…”